The present invention relates to a method of and apparatus for inserting coils into slots formed in the stator core of a dynamoelectric machine and more particularly, to a method of and apparatus for inserting coils into the slots in the stator core of a small-sized dynamoelectric machine such as, for example an electric motor.
In a dynamoelectric machine such as an electric motor, the space factor of the slots in the stator or armature, i.e. the ratio of the sum of the cross-sectional areas of the coil wires received by the slots to the cross-sectional area of the slots, is a very significant factor which affects the performance, e.g. the ratio of the output energy to the input energy, as well as the size of the machine.
For instance, in a large-size electric motor operating with large high voltage electric current such as a current for driving an electric car, it is necessary to employ coil wires having a large diameter and to ensure insulation between adjacent coil wires. In the production of a large-size motor, therefore, the wires are pre-shaped to have the desired cross-section are subjected to an insulating treatment. The pre-treated wires are then put into each slot in the stator core in a one-by-one fashion. To this end, each slot in the stator core is an open type slot having a substantially constant circumferential width over entire radial length thereof. The assembling of such a large-size electric motor, therefore, requires considerable manual labor resulting in a low production efficiency, although a high space factor on the order of 70 to 80% is achieved.
On the other hand, small-sized electric motors such as industrial general purpose motors, operating with comparatively small low voltage electric current, are designed and produced making much of the productivity.
Generally, a small-sized electric motor having a space factor of about 60% exhibits an efficiency generally ranging between 60% and 70%, although more strictly the efficiency depends on the type of the motor. It is also known that about 10% increase of the efficiency is attained by an increase of the space factor to 90%.
However, there has been no effective measures for increasing the space factor so that the users have been obliged to use electric motors having rather low efficiency.
Accordingly, an object of the invention is to provide method of and apparatus for inserting coils, which provides a large value of the space factor in the stator without a reduction in the production efficiency, thereby overcoming the problems of the prior art.
Another object of the invention is to provide method of and apparatus for inserting coils, which enables a reduction in the size of the motor thereby contributing to the saving of natural resources.
To these ends, according to the invention, a method of inserting coils is proposed wherein the coils have a coil wire wound regularly in wire layers automatically inserted into slots in the stator core of a dynamoelectric machine by a coil inserting apparatus, with the method including supplying the coils into the spaces formed between respective adjacent blades of the inserting apparatus, pushing up, by a stripper of the apparatus, the portions of the coils located in an area inside the blades until the coil portions are moved out of an area beyond the ends of the blades so as to insert the coils into closed spaces defined by the walls of the respective slots, blades of the apparatus and the stripper. The coils are forced in the closed spaces into the slots in the stator core, and the coils, received by the slots, are compressed as desired until each coil wire assumes a non-circular cross-section.
According to another feature of the invention, an apparatus for inserting coils into slots in a stator core of a dynamoelectric machine is proposed which includes a plurality of blades disposed along a circle at a predetermined circumferential pitch so as to oppose the ends of the partition walls separating adjacent slots from each other, with a plurality of projections being provided which are capable of projecting into the spaces formed between respective adjacent blades. A stripper is disposed at the center of the circle of the blades and is adapted to push up the coils supported by the blades into corresponding slots of the core fitting around the upper ends of the blades. At least the portions of the projections opposed to the slots in the stator core when the stripper is in the end of its upward stroke, are constituted by pushers which are disposed radially around the stripper for sliding movement in the radial direction. The coil inserting apparatus includes a conical or pyramidal cam disposed at the center of the stripper and contacting one end of the pushers, with a means being provided for moving the cam up and down.
These and other objects, features and advantages of the invention will become more apparent from the following description of the preferred embodiments taken in conjunction with the accompanying drawings.